In future cellular systems like Long-Term-Evolution (LTE) Networks as described e.g. in the 3GPP technical specification TS 36.300v800, evolved UMTS Terrestrial Radio Access Networks (e-UTRAN) have been proposed. For such systems, the possibility of using multihop Relay Nodes (RN) for providing User Equipment (UE) devices such as cellular phones, handheld computers or the like with wireless access to a core network has been discussed but not yet realized. These multihop relay nodes would be connected to a Base Station (BS) of the Network via a wireless link. The multihop relay nodes would provide range extension (coverage) and capacity enhancement (through SNR improvement) for the network and for the user equipment devices.
In such network architectures, each multihop relay node would be hierarchically associated to a higher level relay node or to the base station. This hierarchical organisation entails a high signalling overhead, which can be reduced if control information like bandwidth requests and grants or channel quality information are aggregated in the multihop relay node.
Each multihop relay node should be enabled to independently schedule the resources like bandwidth, time slot resources or code resources provided to it. This local scheduling procedure leads to decentralized (hierarchical) scheduling.
The multihop relay node might apply known fair scheduling schemes e.g. as proposed by H. Kim and Y. Han in: “A Proportional Fair Scheduling for Multicarrier Transmission Systems”, IEEE Communication Letters, Vol. 9, No. 3, March 2005 for the local fair scheduling procedure.
The price of the decentralized scheduling would be that the local distribution of the resources of the multihop relay node would be not visible for higher level units, in particular for the base station scheduler.
As a consequence, the scheduling would be unfair if the base station scheduler would apply a standard fair scheduling scheme treating the multihop relay node in the same way as a local user equipment unit directly accessing the base station. The reason is that the many user equipment units hidden behind the multihop relay node would have to share the same amount of resources one single local user equipment device can dispose of.